Rotor train torsional mode frequency tuning apparatus

ABSTRACT

A rotor train torsional mode frequency tuning apparatus is provided and includes a rotor train and a coupling element. The rotor train includes first and second shafts and a coupling operably disposed between the first and second shafts and has a torsional mode frequency. The coupling element is disposed at the coupling and is configured to adjust the torsional mode frequency of the rotor train by a change in at least one of inertia and/or torsional stiffness in the rotor train.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to a rotor train torsional mode frequency apparatus and, more particularly, to a rotor train torsional mode frequency apparatus in which a rotor train frequency is adjustable by a change in inertia and/or torsional stiffness somewhere in the train.

Rotating bodies, such as rotors, are used in many different types of mechanical and electrical elements, including generators, motors and other similar devices. These rotating bodies have multiple torsional natural frequency modes and for a variety of reasons, including stress, fatigue, performance, etc., it is desirable to keep these frequency modes outside certain operating ranges. For example, generators, or other mechanical elements including a rotating body, typically have at least one torsional natural frequency mode close to twice a line frequency. If this frequency mode becomes too close to twice a line frequency and becomes excited, it can cause failure of elements in a coupled body, such as the last stage buckets in a coupled turbine.

A frequency of a rotor torsional mode can be shifted by changes in either inertia or torsional stiffness that directly impact the frequency of the rotating body mode of interest (i.e., by adding or removing large shrunk-on rings). However, making such changes requires a process of decoupling of the rotor from other rotor sections in the train and exposing the rotor to allow the installation/removal of the rings. The rings are often large, high strength and expensive and, if the process is unsuccessful, components may need to be machined to remove stiffness or inertia depending on the scenario. Each of these steps can be expensive and time consuming.

The processes described above for tuning the frequency of a rotor torsional mode also tend not to target just the torsional frequency or vibration of the rotor modes. Rather, the current processes of mass addition can affect the stresses in the rotor or lead to unwanted lateral frequency changes.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, a rotor train torsional mode frequency tuning apparatus is provided and includes a rotor train and a coupling element. The rotor train includes first and second shafts and a coupling operably disposed between the first and second shafts and has a torsional mode frequency. The coupling element is disposed at the coupling and is configured to adjust the torsional mode frequency of the rotor train by a change in at least one of inertia and/or torsional stiffness in the rotor train.

According to another aspect of the invention, a rotor train torsional mode frequency tuning apparatus is provided and includes a coupling element fixedly disposed on a coupling operably disposed between first and second shafts and a portable mass supportively disposable on the coupling element. The portable mass is movable to the coupling element to adjust at least one of a torsional stiffness and a rotational inertia of one of the shafts such that a frequency of a torsional mode of the one of the shafts is substantially identical to a natural frequency of the torsional mode of the other one of the shafts.

According to yet another aspect of the invention, an apparatus for rotor train torsional mode frequency tuning is provided. The rotor train includes a coupling by which respective ends of shafts are connectable with each other. The apparatus includes a coupling element fixedly disposed on the coupling and a portable mass supportively disposable on the coupling element. The portable mass is movable to the coupling element to adjust at least one of a torsional stiffness and a rotational inertia of one of the shafts such that a frequency of a torsional mode of the one of the shafts is substantially identical to a natural frequency of the torsional mode of the other one of the shafts.

These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic side view of a rotor train;

FIG. 2 is a schematic diagram of a rotor train torsional mode frequency apparatus in accordance with embodiments;

FIG. 3 is a schematic diagram of a rotor train torsional mode frequency apparatus in accordance with alternative embodiments;

FIG. 4 is a schematic diagram of a rotor train torsional mode frequency apparatus in accordance with further alternative embodiments;

FIG. 5 is an axial view of multiple-piece plates or rings that are usable in the embodiments of at least FIGS. 2 and 4; and

FIG. 6 is a flow diagram of a rotor train torsional mode frequency apparatus in accordance with further alternative embodiments.

The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.

DETAILED DESCRIPTION OF THE INVENTION

The description provided below relates to tuning of torsional natural frequencies in, for example, turbine-generator power trains. The disclosure of such tuning is similar to disclosures in U.S. Pat. No. 8,013,481, the contents of which are incorporated herein by reference. The tuning can be applied at a coupling of two shafts or rotors and is provided by a torsional vibration absorber that serves to adjust a rotor train frequency by a change in inertia and/or torsional stiffness somewhere in the train.

With reference to FIG. 1, a rotating body 100 is connected to a mechanical device 102 via a first shaft 105. The rotating body 100 may be a generator rotor, but it is understood that any mechanical element can be used in conjunction with embodiments of this invention. Mechanical device 102 can be any device that is coupled to the rotating body 100, such as a steam turbine, gas turbine, combined gas and steam turbine, etc. The first shaft 105 has an end portion 106 and is further coupled or otherwise connected at the end portion 106 to a complementary end portion 107 of a second shaft 108 by way of a coupling 109. As shown in FIG. 1, the rotating body 100, the first shaft 105 and the second shaft 108 can be supported by any suitable devices, including bearings 104.

The coupling 109 may include a first coupling part 1091, which is associated with the end of the first shaft 105, and a second coupling part 1092, which is associated with the end of the second shaft 108. The first shaft 105, the second shaft 108 and the first and second coupling parts 1091 and 1092 of the coupling 109 of FIG. 1 form a portion of a rotor train 110. With reference to FIGS. 2-4, an apparatus 1 for rotor train torsional mode frequency tuning is provided and is usable with the rotor train 110 or with similar transmissions. As shown in FIGS. 2-4, the apparatus 1 includes a coupling element 2, a stationary element 3 and a portable mass 4. The coupling element 2 is fixedly disposed on the second coupling part 1092 of the coupling 109. The stationary element 3 is disposed proximate to the coupling element 2. The portable mass 4 is supportively disposable on either the stationary element 3 or the coupling element 2.

As will be described is more detail below, the portable mass 4 is re-positionable or movable from one of the stationary element 3 and the coupling element 2 to the other one of the stationary element 3 and the coupling element 2 in order to adjust at least one of a torsional stiffness and a rotational inertia of one of the first shaft 105 and the second shaft 108. More particularly, the portable mass 4 may be moved from the stationary element 3 to the coupling element 2 or from the coupling element 2 to the stationary element 3 in order to adjust at least one of a torsional stiffness and a rotational inertia of the second shaft 108. In so doing, a frequency of a torsional mode of the second shaft 108 can be made substantially identical to a natural frequency of the torsional mode of the first shaft 105.

With particular reference to FIG. 2, the coupling element 2 may be mechanically coupled to the coupling 109. In this case, the coupling element 2 includes a base ring 10, which is mechanically coupled to an outer radial surface 11 of the coupling 109, and a retaining ring 12 that extends axially from the base ring 10. As shown in FIG. 2, the outer radial surface 11 of the coupling element 109, an axial surface 13 of the base ring 10 and an inner radial surface 14 of the retaining ring 12 cooperatively define an annulus 15.

With the above-described arrangement, the stationary element 3 includes a flange 16 and hook elements 17. The flange 16 is disposed proximate to the coupling element 2 and the hook elements 17 are arrayed on the flange 16 to support or hold the portable mass 4. Where the portable mass 4 is provided as an annular inertial plate 18 or ring, the portable mass 4 can be lifted off of the hook elements 17 and loaded onto the coupling element 2. In accordance with embodiments, the portable mass 4 may be provided as a complete annular element or as multiple circumferentially segmented pieces assembled together and may be sized to fit inside the annulus 15.

The loading may involve transporting the portable mass 4 from the flange 16 and the hook elements 17 to the coupling element 2 and then sliding the portable mass 4 into the annulus 15. Such loading can be completed without decoupling the second shaft 108 from the first shaft 105, without decoupling the first shaft 105 from the mechanical device 102 or the rotating body 100 and without decoupling the second shaft 108 from any downstream body to which the second shaft 108 may be attached.

In accordance with further embodiments, the portable mass 4 may be provided as a plurality of portable masses 4 each having similar or unique individual masses or weights. As such, a customizable accuracy and precision of the adjustment of the at least one of the torsional stiffness and the rotational inertia of the second shaft 108 can be achieved by loading one or more portable masses 4 into the annulus 15.

During an operation of the rotor train 110 of FIG. 2, rotation of the first shaft 105 drives a corresponding rotation of the second shaft 108 and the portable mass (or masses) 4. The portable mass (or masses) 4 are thus contained within the annulus 15 by the retaining ring 12 and by centrifugal forces generated between the portable mass (or masses) 4 and the inner radial surface 14 of the retaining ring 12. Additional containment of the portable mass (or masses) 4 may be provided by fastening elements optionally disposed to fasten or bolt the portable mass (or masses) 4 to the base ring 10.

With particular reference to FIG. 3, the coupling element 2 may be press fit onto the coupling 109. In this case, the coupling element 2 includes a base ring 20, which is configured to be shrunk fit onto an outer radial surface 21 of the coupling 109, and which includes an axial portion 22 and a radial portion 23. As shown in FIG. 3, an outer radial surface 24 of the axial portion 22 and an axial surface 25 of the radial portion 23 cooperatively define an annular pocket 26.

With the above-described arrangement, the stationary element 3 includes an end face 27, which is disposed proximate to the coupling element 2 and configured to support or hold the portable mass 4. Where the portable mass 4 is provided as an annular inertial plate 28 or ring, the portable mass 4 can be lifted off of the end face 27 and loaded onto the coupling element 2. In accordance with embodiments, the portable mass 4 may be provided as a complete annular element or as multiple circumferentially segmented pieces assembled together and may be sized to fit in the pocket 26.

The loading may involve transporting the portable mass 4 from the end face 27 to the coupling element 2 and then sliding the portable mass 4 in the pocket 26. Such loading may be completed without decoupling the second shaft 108 from the first shaft 105, without decoupling the first shaft 105 from the mechanical device 102 or the rotating body 100 and without decoupling the second shaft 108 from any downstream body to which the second shaft 108 may be attached.

In accordance with further embodiments, the portable mass 4 may be provided as a plurality of portable masses 4 each having similar or unique individual masses or weights. As such, a customizable accuracy and precision of the adjustment of the at least one of the torsional stiffness and the rotational inertia of the second shaft 108 can be achieved by loading one or more portable masses 4 in the pocket 26.

During an operation of the rotor train 110 of FIG. 3, rotation of the first shaft 105 drives a corresponding rotation of the second shaft 108 and the portable mass (or masses) 4. The portable mass (or masses) 4 are thus contained in the pocket 24 by the axial portion 22 and by centrifugal forces generated between the portable mass (or masses) 4 and the outer radial surface 24 of the axial portion 22. Additional containment of the portable mass (or masses) 4 may be provided by fastening elements optionally disposed to fasten or bolt the portable mass (or masses) 4 to the radial portion 23.

With particular reference to FIG. 4, the coupling element 2 may be integrally formed with the coupling 109. In this case, the coupling element 2 includes the first coupling part 1091 and the second coupling part 1092 (see FIGS. 1 and 4). As shown in FIG. 4, an axial surface 30 of the first coupling part 1091, an axial surface 31 of the second coupling part 1092 and a radial surface 32 of the second coupling part 1092 cooperatively define an annular recess 33.

With the above-described arrangement, the stationary element 3 includes a flange 34 and hook elements 35. The flange 34 is disposed proximate to the coupling element 2 and the hook elements 35 are arrayed on the flange 34 to support or hold the portable mass 4. Where the portable mass 4 is provided as an annular inertial plate 36 or ring, the portable mass 4 can be lifted off of the hook elements 35 and loaded onto the coupling element 2. In accordance with embodiments, the portable mass 4 may be provided as a complete annular element or as multiple circumferentially segmented pieces assembled together and may be sized to fit inside the recess 33.

The loading may involve transporting the portable mass 4 from the flange 34 and the hook elements 35 to the coupling element 2 and then sliding the portable mass 4 into the recess 33. Such loading can be completed without decoupling the second shaft 108 from the first shaft 105, without decoupling the first shaft 105 from the mechanical device 102 or the rotating body 100 and without decoupling the second shaft 108 from any downstream body to which the second shaft 108 may be attached.

In accordance with further embodiments, the portable mass 4 may be provided as a plurality of portable masses 4 each having similar or unique individual masses or weights. As such, a customizable accuracy and precision of the adjustment of the at least one of the torsional stiffness and the rotational inertia of the second shaft 108 can be achieved by loading one or more portable masses 4 into the annulus 15.

During an operation of the rotor train 110 of FIG. 4, rotation of the first shaft 105 drives a corresponding rotation of the second shaft 108 and the portable mass (or masses) 4. The portable mass (or masses) 4 are thus contained within the recess by centrifugal forces generated between the portable mass (or masses) 4 and the axial surface 31 of the second coupling part 1092. Additional containment of the portable mass (or masses) 4 may be provided by fastening elements (e.g., bolts) 36 disposed to fasten or bolt the portable mass (or masses) 4 to the second coupling part 1092.

In accordance with further embodiments and, with reference to FIG. 5, it will be understood that at least the inertial plates 18 of the embodiments of FIG. 2 and the inertial plates 36 of the embodiments of FIG. 4 may be provided in multiple pieces such as the segments 50 and 51 of FIG. 5. These segments are connectable with one another along seam 52 and may provide for simpler installations of the portable mass 4 in each of the corresponding cases. In addition, the use of the segments 50 and 51 may permit the removal of or allow for the absence of the stationary element 3 from the embodiments of at least FIGS. 2 and 4. In these cases, the segments 50 and 51 could be respectively stowed or maintained nearby or proximate to the coupling element 2 and separately disposed on the coupling 109. Once such disposition occurs, the segments 50 and 51 can be tied or otherwise coupled together to form the inertial plates 18 in the annulus 15 (see FIG. 2) or in the recess 33 (see FIG. 4).

With reference to FIG. 6, a rotor train torsional mode frequency apparatus in accordance with further alternative embodiments is provided. As shown in FIG. 6, the coupling element 2 is disposed at the coupling 109 as described above and is provided as a re-configurable mass 40. As such, all or a portion of the mass of the coupling element 2 may be moved, extended or stretched along axial or radial dimensions in accordance with a desire or need to adjust the at least one of the torsional stiffness and the rotational inertia of the second shaft 108. In accordance with embodiments, the re-configurable mass 40 may include a morphing or smart material, such as a shape memory alloy (e.g., nickel-titanium alloy) or a shape memory polymer. In these cases, a configuration of the coupling element 2 can be changed by an application of heat or electricity.

The embodiments described above add torsional inertia over or between the coupling 109 in the rotor train 110. This change in inertia yields a torsional natural frequency of oscillation in the second shaft 108 that is substantially identical to the torsional frequency of interest in the first shaft 105 and is obtained using modifications of a fully assembled unit. In addition, since the modifications are being done to a fully assembled unit, the modifications allow for result verification and further modifications, if necessary.

While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims. 

1. A rotor train torsional mode frequency tuning apparatus, comprising: a rotor train comprising first and second shafts and a coupling operably disposed between the first and second shafts, the rotor train having a torsional mode frequency, and the apparatus further comprising: a coupling element disposed at the coupling and being configured to adjust the torsional mode frequency of the rotor train by a change in at least one of inertia and/or torsional stiffness in the rotor train.
 2. The apparatus according to claim 1, wherein the coupling element comprises a re-configurable mass.
 3. The apparatus according to claim 1, wherein the coupling element comprises a re-positionable mass.
 4. The apparatus according to claim 1, further comprising: a stationary element disposed proximate to the coupling element; and a portable mass supportively disposable on the stationary element or the coupling element.
 5. The apparatus according to claim 4, wherein the coupling element is at least one of mechanically coupled to the coupling, press fit onto the coupling and integrally formed with the coupling and wherein the portable mass comprises an annular plate.
 6. A rotor train torsional mode frequency tuning apparatus, comprising: a coupling element fixedly disposed on a coupling operably disposed between first and second shafts; and a portable mass supportively disposable on the coupling element, the portable mass being movable to the coupling element to adjust at least one of a torsional stiffness and a rotational inertia of the second shaft such that a frequency of a torsional mode of the second shaft is substantially identical to a natural frequency of the torsional mode of the first shaft.
 7. The apparatus according to claim 6, wherein the coupling element is at least one of mechanically coupled to the coupling, press fit onto the coupling and integrally formed with the coupling.
 8. The apparatus according to claim 7, wherein the portable mass comprises an annular plate.
 9. An apparatus for rotor train torsional mode frequency tuning, the rotor train comprising: a coupling by which respective ends of shafts are connectable with each other, the apparatus comprising: a coupling element fixedly disposed on the coupling; and a portable mass supportively disposable on the coupling element, the portable mass being movable to the coupling element to adjust at least one of a torsional stiffness and a rotational inertia of one of the shafts such that a frequency of a torsional mode of the one of the shafts is substantially identical to a natural frequency of the torsional mode of the other one of the shafts.
 10. The apparatus according to claim 9, wherein the shafts comprise: a first shaft coupled to a turbomachine; and a second shaft coupled with the first shaft via the coupling.
 11. The apparatus according to claim 10, wherein the coupling comprises: a first coupling part associated with the end of the first shaft; and a second coupling part associated with the end of the second shaft, the coupling element being fixedly disposed on the second coupling part.
 12. The apparatus according to claim 9, wherein the coupling element is mechanically coupled to the coupling.
 13. The apparatus according to claim 12, wherein the coupling element comprises: a base ring mechanically coupled to the coupling; and a retaining ring extending axially from the base ring, an outer radial surface of the coupling element, an axial surface of the base ring and an inner radial surface of the retaining ring defining an annulus, wherein the portable mass comprises an annular plate sized to fit in the annulus.
 14. The apparatus according to claim 13, wherein the rotor train comprises a stationary element disposed proximate to the coupling element, the portable mass being supportively disposable on the stationary element or the coupling element and movable from one to the other of the stationary element and the coupling element.
 15. The apparatus according to claim 9, wherein the coupling element is press fit onto the coupling.
 16. The apparatus according to claim 15, wherein the coupling element comprises: a base ring shrunk fit onto the coupling, the base ring including an axial portion and a radial portion, an outer radial surface of the axial portion and an axial surface of the radial portion defining a pocket.
 17. The apparatus according to claim 16, wherein the portable mass comprises an annular plate sized to fit in the pocket.
 18. The apparatus according to claim 9, wherein the coupling element is integrally formed with the coupling.
 19. The apparatus according to claim 18, wherein the coupling element comprises: a first coupling part associated with the end of the first shaft; a second coupling part associated with the end of the second shaft, an axial surface of the first coupling part, an axial surface of the second coupling part and a radial surface of the second coupling part defining a recess.
 20. The apparatus according to claim 19, wherein the portable mass comprises an annular plate configured to be bolted into the recess. 